Attempts at measurement of the magnetic properties of ferromagnetic materials at very low flux densities showed inconsistencies which were attributed either to errors in methods or to some behavior of the material. Check tests, using the same procedure in each case, eliminated the first supposition. The results of this investigation show that, with a steel of medium silicon content tested at 10 gausses over a period of 24 hours, there exists a 5 to 15 percent decrease in permeability. On the average, 50 to 60 percent of this drift occurred within one hour after demagnetization and none after 24 hours.